1. Field of the Invention
This invention relates to a method of partial reproduction of a pattern from a master sheet or the like.
2. Description of the Prior Art
Xerography is one of the prior art techniques of image reproduction and comprises (a) preparing an image receiving plate by coating a thin layer of photoconductive material such as selenium on one surface of a plate of electrically conductive material such as aluminum, (b) uniformly charging the photoconductive surface of the image receiving plate with positive electrostatic charges by a corona discharge, (c) projecting an image carried by a master sheet to be reproduced onto the image receiving plate for forming an electrostatic latent image on the photoconductive surface of the image receiving plate, (d) applying a negatively charged toner contained in an insulating liquid or on a dry carrier to the latent image for turning the latent image into a visible image, (e) electrostatically transferring the developed image to a sheet, and (f) heating the sheet to fix the transferred record.
In an attempt to reproduce only specific areas of an image recorded on a master sheet, various methods have been hitherto proposed. According to one of the known methods, a masking sheet suitably cut out at areas corresponding to the desired areas of an image to be reproduced is superposed on the master sheet for the purpose of optically shielding the undesired image portions recorded on the master sheet. According to another known method, a grounded electrode plate suitably cut out at areas corresponding to the desired areas of an image to be reproduced is interposed between a corona discharge electrode and photoconductive surface of the kind above described, and the corona discharge is applied to the photoconductive surface through the cut out grounded electrode plate for partially forming an electrostatic latent image consisting of the desired areas.
However, these prior art methods are defective in that a great deal of inconvenience is encountered in the copying of master sheets and the copying operation cannot be easily carried out due to the fact that the partial reproduction of images on different master sheets requires preparation of a corresponding number of masking sheets or grounded electrode plates cut out to conform to the different patterns and since such sheet or electrode plate must be replaced by another each time the partial reproduction is carried out on a different master sheet.
The known methods above described may be fairly satisfactory when a portion other than a free central portion of the image on the master sheet is partially reproduced. When, however, it is desired to selectively shield only the free central portion of the image on the master sheet and to reproduce the remaining image portions, extreme difficulty is encountered with the prior art methods in the manner of supporting the shielding means because the central portion only of the image on the master sheet must be shielded.